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Title Preparation of 1-C14-Propene-1 and the Mechanism of Permanganate Oxidation of Propene
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Author Fries, B.A.
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I 1· , . BERKELEY, CALIFORNIA ·. ENG-48 INDEX II 0 • UCRL 19 This document contai-n-s--·,...... 2.,.O--p-g-.s'--;-'- and 0 plates of figureS:--- This is-Copy~of 76 • Series A I DO NOT Ii.E''[tOVE TUS PAGE Issued to: INFORMATION DIVISION ~ilitl~~;t;:_:,.;:.p',!~~:~"Cr ."~~-F' ~"""'i"'~-:~"~i'T 1. This .document contains restricted data withinClt~~SI~e~~g~LQt'itl;~.·AtgJ:i~Ut'N~1-''CV Act of :1,.946 and/or informu.tion affecting tho ndt"1artitF'ds1Censie>~fr,tlwcJJn,itl:l'd:'"" States within the meaning of the Espionage Act u. S. C. 31 & 32, as amended. Its transmission or the revelation of its contents in 8.n'-' manner to an un:J.utl-\'.)r~ il';ed perscm is prohibited'and may result in' severe crimi~,al penalty.:-----.----- 2. Before this dOClUTlentcan begiventoa person toread~ hiS name must be ..,n the Heading List of those authorized to read material on this subject, or permissic must be obtained from the Information Division or the £~ecutive Office. 3. 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I ...1l.o.....-..--j,-L;'-"-'--f-J..LLJ+'/UIr.rK ------j--.-.-----I .----.--I~- ~~ --·--1------··-- -._------..-t------.------,----.----~----.--.- -.------J------.------~------.-.-- 1 ' ------.. ------. --- ~r--,-.------~--.------I I --+-----+---I~---]~-~------~~--~--.----~~ -~------.--~~- --.-- - .. -I --'----. -+.._L -I-- -' A·-l6 UNIVERS~TY OF CALIFORnIA RADIAT!ON LABORATORY Contract No. W-7405-Eng .-48 PREPARATION OF l-C14_PROPENE-1 AND THE MEQHANISM OF PERMANGANATE OXIDATION OF PROPENE by B. A. Fries and M. Calvin 10 December 1947 This document contains restricted data within the mean ing of the Atomic Energy Act of 1946 and/or information affecting the national defense of the United States within the meaning of the Espionage Act U.S.C. 31 & 32, as amended. Its transmission or the revelation of its contents in any manner to an unauthorized person is prohibited and may result in severe criminal penalty. Berkeley, California ,UCm. 19 " "j' X.~i ,' ..""," -'f t. , Chemistry-General -2- Standard Distribution UCRL 1~ Serie~/A: No. Copies.. / .- / ,) Argonne National Laboratory 10 Atomic Energy Commission 3 // _ /'3 Battelle Memorial Institute 1 /1-/ Brookhaven National Laboratory 10 /,;- ..2,1 Carbide & Carbon Chemicals Corp. (K-25 Area) 2 ::2 s·- .' ,;I (f' Carbide & Carbon Chemicals Corp. (Y-12 Area) 2 Clinton Laboratories 12 Io/C) f/ (/ General Electric Company 4 Hanford Engineer lrTorks 2 '-I .(;, ,c< Iowa State College 1 <-J 7 Los Alamos 3 Madison Square Area 1 Massachusetts Institute of Technology 1 Monsanto Chemical Company, Dnyton 1 _,ff' National Bureau of Standards 2 ,-S:"t'!.,Ji ",<, ••':..:3 Patent Advisor 1 Research Division (for NEPA), Ouk Ridge 1 Research Division, Ollie Ridge 15 University of California, Radiation Laboretory '73 Chemistry 1 W. M. Latimer 1 ") 'l .' I.~' ~ "I (" Information Division 2 f .~;) TOTAL ~ Radiation Laboratory University of California Berkeley, California -3- ~- UCRL-19 ABSTRACT PREPARATION OF l-C~4_PROP}<~HE-l AND THE MECHANISM OF P~RMANGANATE OXIDATION OF PROPENE by B. A. Fries and M. Calvin From the Radiation Laboratory and Department of Chemistry, University of California; Berkeley. 10 December 1947 ABSTRACT •. l-C14_propene~1 has been prepared. The migration of the double bond under a variety of experimental conditions in the preparation of propene has been investigated. 'rhe mechanism of the permanganate oxi- dation of the labelled propene has been examined; it has been found to proceed by several paths, the relative importance of which depends upon the experimental conditions .. especia lly the pH. Contract No. W-7405-eng-48. For pUblication in J. Am. Chem. Soc. UCRL-l9 PREPARATION OF l-C14_PROPENE-l AND THE MECHANISM OF PERMANGANATE OXIDATION OF PROPENE* by B••A Fr1es• ** an.d M Cal·V1n From the Radiation Laboratory and Department of Chemistry, University of California, Berkeley_ 10 December 1947 The preparation of l-C14_propene_l was undertaken in order to have available propene labelled in a terminal position and, incidently, to study the stability of the double bond when preparing propene under a variety of conditions. During the course of this investigation, a re- liable procedure for the degradative analysis of the propene had to be developed. This analytical problem led to a study of the oxidative degradation of propene with permanganate. A number of methods were available for the preparation of propene. Several of these methods were tried with 014 labelled materials, while others were discarded when preliminary tests with nonradioactive materials indicated either very poor yields or impure products. The first three • Our thanks are due to Mrs. Martha Kirk for her technical assistance in this work and particularly for the performance of many of the isotopic analyses. ** While on leave from California Research Corporation, Richmond, Cali fornia. -5- UCRL-19 It 11 of the following methods were actually en:ployed for radioaotive propene synthesis. 1) Dehydration of n-propanol with metaphosphoric acid 2) . Dehydration of n-propanol ov~r heated alumina 3) Pyrolysis of n-propyltrimethylammonium hydroxide 4) Pyrolysis of methyl n-propyl xanthate 5) Dehydrobromination of n-propyl bromide with alcoholic KOH Extensive rearrangement of the double bond was found to occur when pre- paring propene by dehydration with metaphosphoric acid and with heated A1 203 • However, the pyrolysis of the quaternary ammonium base gave little, if any, rearrangement and the product consisted principally of l4 c~\ l-C _propene-l (CH3-CH=tH2), wher-ea s in the other ses, mixtures of l-C14_proDene-l and 3-c14 _proDtme-l (~H3-CB=CH2) were obtained. Degradation Procedure The important features desired in the degradative process include. 1) minimum number of operations 2) easy separation of the products of the degradation reaction 3) unequivocal identification of the origin of these products. Here again several choices were available, among them, oxidative degrada- tion with permanganate and dichromate, ozonolysis, and glycol formation with hydrogen peroxide and subsequent oxidation and splitting of the glycol with periodate. Ozonolysis of propene gives rise to a mixture of formaldehyde and acetaldehyde, which are not too easily separated. Preliminary glycol formation and periodate oxidation also yields these same two aldehydes and in addition involves more manipulation. -6- UCRL-l9 ~manganate OXid~tion of ~!2pene. Acid permanganate oxidation should produce acetic and carbonic acids if propylene glycol is an intermedtate, This appeared to be a satisfactory procedure, particularly since Evans (1) reported that propylene glycol was converted quantitatively to acetic acid and CO 2 with neutral permanganate at 50 oC, although in the presence of alkali, oxalic acid was formed, Hence, examination of the acetic and carbonic aoids for 014 should indicate the extent of labelling of the two term- inal carbon atoms of the propene. Howe~er, rearrangement of the double bond might also occur dUring the analysis, but this could not be deter- mined until some radioactive propene had been prepared. Although per- manganate oxidation was chosen for the degradative analysis, in one instance ozonolysis was employed to confirm the results of the perman- ganate method. The following procedure was first tested with non-radioactive propene. Approximately three millimoles of propene was introduced into an evacuated 3-necked flask of about 385 mI. volume. Fifty mI. of water or buffer solution was added through a dropping funnel. An in duction stirrer was used to agitate the aqueous phase. An amount of 0.4 N K1~n04' calculated to be just sufficient to oxidize propene to propylene glycol, was added over a period of 45 minutes. This was followed by the addition of 110 percent of the amount of 2N KMn04 re quired for the oxidation of propylene glycol to acetic and carbonic acids. this addition required 45 minutes, after which the solution was stirred 15 minut~s more. An H2S04-acidified solution of FeS04 was added to reduce all manganese to the manganous state and simultaneously liberate CO 2, The flask was connected to a NaOH absorber and swept with nitrogen gas to collect this C02 fraction. The solution remaining was steam distilled to recover acetic acid. This latter was titrated with NaOH and evaporated to dryness as sodium acetate. The weight of the salt obtained, when oompared with the titration value, indicated that the salt was the acetate. This procedure was studied at several values of pH and at two temperatures. The results are shown in Table I. 1. W. L. E.'vans, J. Am. Ghem. Soc., 45, 171 (1923). .. ) ,------./ -7- UCRL-19 TABLE I It can be seen that in weak acid solution about 70% of the theoret- ioal amount ,-,f aC"Jtic ar.id and 90% of the theoretical amount of carbonic acid may be recovered. This calculation was based on the splitting of propene at the double bond to yield equimolar amounts of acetic and car- bonic acids. There was no significant change in yield of these two fractions on dec"easing the pH from 6 to 4 and stronger acid w~s avoided to reduce tre possibility of a shift of the double bond in propene during the analysis. In the subsequent use of this procedure with the various samples 0' radioactive propene. the reaction was carried out at pH 4 and at roor;) :emperature. Inasmuch as the total carbon recovery in the C02 and acetic acid fractions was quite low (70-80%) an attempt was made to locate the missing carbon. The solution remaining after steam distillation of the acetic acid was made 6 N in H2S04 and 0.5 M in Cr03' heated to boiling and swept with oxygen for one hour. Considerable carbon and C14 activity was found in this fraction. The inclusion of this additional carbon boosted the total carbon recovery to 85-90%. -8- UCRL-19 There were several indications that this oxidizable residue was oxalic acid. First, oxalic acid ,may be found during alkaline permangan- ate oxidation of p~opylene glycol (1). Second, oxalic acid is oxidized very slowly at 25°0 and pH 4 by KMn04 or Mn02 and therefore, the oxalic acid would be stable, if present. Third, the nature of the analytical procedure eliminates the possibility of a one carbon compound, since these compounds (CH30E, HCHO, HCOOH), if not completely oxidized by the perman- ganate, would be volatilized during the steam distillation. In addition, subsequent specific activity determinations of this fraction (see Discus. sion) eliminated the possibility of a three carbon compound and corresponded well With a two carbon substance. Hence, this residue was either oxalic, glycolic or glyoxylic acid~ The last two of these may be intermediates in the formation of oxalic acid. Ethylene glycol also satisfies the chemi- cal properties set for the residue, but it is difficult to see why this glycol should remain unoxidized while propylene glycol is apparently com- pletely reacted. In one experiment with radioactive propene, the isolation of oxalic acid was attempted. After the addition of the last permanganate, all man- ganese was removed as Mn02 by centrifugation. Inactive sodium oxalate was added as a carrier and the oxalate was ultimately preoipitated as CaC 204 after separation from phosphate by employing the scheme of Swift (2). ~./ .. The completeness of recovery of oxalate could not be accurateiy determined, but appeared to be nearly quantitative. Powever, since the calcium salts of glycolic and glyoxylic acid are relatively insoluble~ they might be carried down with the CaC204' The CaC204 was titrated with permanganate 2r E. H~ Swift, A SyetE'lm of Chemical Ji.nalysis, Prentice-Hall, Inc., New York, 1940, pr 469 et. seq. -9- UCRL-19 in the UBual manner J and the C02 was collected and analyzed for C14 activity. The titration agreed within 3 percent with the formula CaC 204 for the calcium precipitate; however, since the amount of carrier was about four times the amount of oxalate expected, the presence of other insolublE calcium salts might have been masked. The amount of C14 found as oxalate was about 70% of the amount fO'Llnd by direct Cr03 oxidation of the residue in another experiment using the same radioactive propene. Ozonolysis Method. A highly refined procedure was not developed but the following scheme gave a satisfactory check with the result of the acid permanganate oxidation. About trree millimoles of propene was transferred to the ozonolysis vessel, 15 ml. of ethyl chloride was added and the vessel immersed in a dry ice-aoetone bath~ A current of oxygen containing 2-3% ozone was bubbled through the solution until the solution turned blue (indicating excess ozone). The vessel and contents were warmed to OOC and 10 mle water added and sha1<:en with the ethyl chloride. The ethyl chloride was removed by evaporation under house vacuum. The aqueous solution, which now contains formaldehyde and acetaldehyde J was made alkaline with NaOH. Excess KMn04 was added and the solution heated to 500C. The formaldehyde was oxidized to C02 while the acetaldehyde was oxidized to acetic acid. From this point on J the analysis was carried out in the same manner as the permanganate procedure. In this ozonization some propene probably was swept out of the solution by the current of oxygen, while some of the aldehydes were lost during the evaporation of ethyl chloride. In addition some ethyl chloride re- ma ined in the aqueous phase and was oxidized to acetic acid. Preparation of l-C14-n_Propanol (CH3-EH2-CH20~)* -~.. ~ The principal intermediate in the synthesis of propylene was propanol. The starting point of this synthesis was BaC03 containing C14 from which C140 2 was obtained. The follOWing series of reactions out line the procedure by which n-propanol was prepared. 1) -10- UCRL-19 5) * HZ * CH3-CHZ-COOCHZ-CH2-CH3 .."., -4 CH3-CHZ-CHZOH Cu chromite The procedure for carbonation of Grignard reagent in a vacuum system has been desoribed (3). In the present case, the ethyl mag~esium bromide was prepared under nitrogen and 25 millimoles of the. reagent wa~ transferred with a syringe into a flask connected to the vacuum line. The CO 2 was gen- erated by the addition of conoentrated H2S04 to 4.1Z gms. (20.9*millimoles) of BaC03 containing approximately 800 miorocuries of C14, The C02 was re covered in a trap cooled with liquid nitrogen and then allowed to distill into the Grignard reagent held at -200 C. vvhen the absorption of carbon dioxide was complete, the solution was cooled to -800 C and the Grignard compound decomposed by the addition of dilute H2S04 and warming. The ether was evaporated under house vacuum, bromide ion was precipitated by the addi tion of exoess AgZS04 and the solution steam distilled to recover propionic acid. After titration with NaOH, the solution was evaporated to dryness and solid sodium proprionute was recovered with 94.8% yield. A very high specific activity product was not required in this experiment and a large dilut:.on of C14 activity could be tolerated. Consequently, the reduction of the acid to alcohol was carried out on the n-propyl ester. The use of this ester eliminated the subsequent separation of two aloohols following the hydrogenation. The esterification was carried out on a 40 millimole scale b~' adding inactive sodium proprionate to 1.62 gms. (16.8 millimoles) of the r~dioactive salt. The esterification was driven to completion by azeotropic distillation. The solid salt was refluxed for several hours with a mixture of 9.0 ml. of n-propyl alcohol, 10.0 mI. of benzene and 1.1 mI. of concentrated sulfuric aoid. ,vater was removed as the ternary azeotrope (68.50 C) with n-propyl alcohol and benzene. A 16 inch, 6 rom. I.D. vacuum jac~eted, unpacked column was used for the distillation. ~~en the tempera ture of the distillate reaohed 740C, the flask was cooled and 1.0 gms. of CaC03 was added to destroy excess H2S04, The distillation was continued, the remaining benzene being removed as Ue binary azeotrope (77.10 C) with n-propyl alcohol. The distillation was stopped when the temperature reached 9Z oc. The ester-alcohol solution remaining was removed from the CaS04 ... CaC03 residue by vacuum transfer. This solution, about 8 ml, was pipetted into a high pressure hydrogenation bomb (Aminco, 43 mI. size) containing Z.O gms. of copper chromite catalyst (Adkins). The bomb was charged with 2500 p.s.i. of H2, heated to 2500 C and maintained there for nine hours. The contents of the bomb were transferred on the vacuum line into a flask containing CaO where the alcohol was dried. The alcohol was again transferred on the vacuum line into a small distilling flask and fractionally distilled using the column desoribed above. The fraction boiling from 96-970 C was recovered. The fraction boiling below 960C (about Z mI.) was returned to the distilling flask with 2.5 mI. of n-propyl alcohol and the mixture redistilled. This 3. W. G. Dauben, J. G. Reid, and P. E. Yankwioh, anal. Chem. 1947. -11- UCRL-19 was repeated again with 2.0 mI. of n-propyl aloohol. The 96-97°0 fraotions were oombined with the first fraotion colleoted. In this manner 10.3 ml. of l-C14-n-propyl alcohol w%>s obtained .J-he indiv:i.dual steps in the above procedure were tested first with inactive ~,terials. these tests gave yields of 90~95% for the carbonation of ethyl magnesium bromide and 95% for the es terification and hydrogenation when measured bJ saponification. In the radioactive s;ynthesis, the carbonation yield was 95%. The chemical yield:;; of the other steps were not checked because the amount of alcohol which re mained with the ester after azeotropic distillation was not known. The yields and losses of C14 in var ious fractions are shown in Table II. The final product contained 4.58 x 106 c/min/mi. or about 50l'c/ml. TABLE II C14 Yields and Losses in Preparation of 1-014-n-propanol ---- . __ _.-.._~- -_._._ ------.-----:-..-.-~_.._-- -_ _ .._- ··-----_··-----1 I Sample \ Total o/min. \ % j' ------.--.--- ..---.----.--.--- - .. --.------1-. _..- -_..__. '-" ....._L •._-_. 7 Starting BaG03 i 7.63 x 10 I I Residue 1 Grignard residues I 4.05 x 104 ,0.6 , I _~_~d ~~.. !r~!~ ona ::"(~~~_8~_.~=.~.~d).. __._ _ _~_._~~_._ ~_~?~ __ ._ J Starting sodium propionate for esterif~cation 5.94 x 107 ~:'4-1 Residue 2 Azeo. dist. 67-740 fruation 0.14 x 107 I Residue 3 Azeo •. dist. 74-92 0 fraction O.ll x 107 1.9 I Residue 4 Fina 1 dist. residues 0.57 x 107 9.6 I ! Final n-propanol 4.72 x 107 79.5 I C14 material balanoe 93.4 I l .. ~.. -, .. _. -_. ~.~ ..._.... -- -'-" -,-.- .~---~ •.... ~-.- .._- '" .J ._._._._t Preparation of 1-c14-n-propyl brom-ide.- The propyl bromide was prepared from n-propanol by the"phosphor'li'san"if bromine method (4), but additional phosphorus and Br2 were added. lhe yield of propyl bromide was 76% bb.sed on propaYlol. A low C14 activity sample of propanol wa s prepared by di lution of the high activity material for use in this prepBration. ------.---_.-.-.----_.,--- 4. 11.. Ii •. Bl[ttt~ Org&nio ,sJ'ntheses. Colleotive Vol. I, Johnviley and Sons, Inc., New York, 1941, p. 37. -12- UCRL-19 Dehydration of n-propanol with Metaphosphoric Acid. A 2 ml. sample of propanol containIng 6350 cfro 014 per" millimole of-alcohol (prepared by dilution of the high activity product) was dehydrated to propene by dropwise addition of tre alcohol to 3 mI. of metaphosproric acid at 2500 0 accordin8~ to the method of Newth (5). iVater and alcohol were condensed in a trap at -20 C while the propene was passed trrough Lrierits o then condensed in a dry 1ce trap, vonsiderable alcohol distilled out of the flask without reacting and the yield of propene was 40% based on the starting propanol. The gas sample was analyzed by mass spectrometer (*). 'rhe analysis of the gas showed 80% propene, 9% butenes, 9% butanes and pentanes and 1% pentenes and hexenes. The propanol was analyzed by mass spectrometer and found to be 99.5% pure; the impurity may have been butyl alcohol. Dehydration of n-propanol over heated Ala03' A 2 mI. portion of the above dilute propanol was dehydrated by dropwise add~tion over a period of 30 minutes into a vertically mounted quartz furnace tube containing A1203 at 3900C. The A1203 was 12-24 mesh Aloreo Alumina (Aluminum Company of Amer~ca, Grade F-l) packed in a bed 23 cm. long and 0.7 em. in diameter. Traps were arranged as in Ue previous experiment. Continuous nitrogen sweeping was maintained to reduce the residence time in the catalyst. The contact times was approximately 5 seconds. A second .samPle of aloohol was de.hydrated over laborator~ prepared A1203 obtained by precipitation of AI(OH)3 from reagent grade Al(N03)g. The catalyst temperature was 4150 C while the contact time was only 2 seconds. The analysis of the first of th~se gas samples was 97% pro~ene and 3% butenes, while the second gas sample contained 95% propene, 3.5~ butenes, 0.5/0 propane and 0.5% n-butane. The yield of propene was about 95% in both cases. Py~olysiB of n-Propyltrimethylammonium hydroxide. The quarternary ammonium brpmide '0as preparadby the'additin of 5 ml:~n-propyl bromide (containing 8300 elm Cl,4/millimole) to exoess ., CH3hN in alcohol and refluxing for several hours. The solvent was evaporated the bromide dissolved in water and excess freshly prepared AgZO was added to convert the bromide to hydroxide. After filtering AgBr and excess Ag20 the aqueous solution was boiled to dryness in a system containing a cold water concensor, a 1 N HCl wash bottle to remove (CHg)gN, a tube of Drierite and a :iquid N2 trap to condense propene. The system was swept with nitrogen d~ring the heating. fhe yield of propene was approximately 90%. Analysis of the gas sr'owed 99% propene, 0.5% butenes and 0.5% ethylene. Pyrolysis ~ Met~l} n-propyl Xantha~. The procedure of &churmann and Boord (6) w.as employea for preparing the.' xanthate ester, however. ' the final ester was not purified by vacuum distillation as carried out by these authors. The decomposi tion of the ester took place very slowly and after boiling for 24 hours, only half the ester was decomposed. The system was swept with a slow current of nitrogen and the gaaes were passed ~:rrough a IN NaOH wash bottle to remove COS and CHgSlf, then through a drying tube and fina lly into a liquid N2 trap. The yield of propene was about 25% and the has composition was 56% propene, g8% butenes, 1.4% ethene, 14% COS while the remainder of the gas oonsisted of several sulfides and merceptans. This method of 'propene preparation, besides giving a gas difficult to free of sulfur compounds also contained an extraordinarily large amount of butene. The use of this method was not attempted with radioactive propanol. * All gas samples were analyzed by mass spectrometer by Dr. N. Bauer, through the courtesy of California Researoh Corporation, Richmond, California. 5. ~. S. Newth, J. Chem. Soc. 79, 915 (1901). 6. I .. Schurmann and C. E. Boord-;-J. Am. Chem. Soc. ~. 4930 (1933). -13- UCRL-19 Lehydrobromination of n-propyl bromide with a'1coh01ic KOH. Propene was pre pared" by refluxing the bro0icf6 Wi"th exceSS'" K6"H dissoIiTed"in absolute ethanol in a system similar to the-se despribed above. 'l'h(; yield of nropene was about 10%, the bulk of the producJe being ethyl-propyl ether. Nef (7) reported a yield ~nalysis of 20% propene. c1 the gas sample showed 75% propene, 16% butenes f 3% i-butane, 3% ethyl propy:i. ether and traces of ethane, propane and propyl bromide • .l.'he use of tris method was not attempted with radioactive propyl bromide. Results and Disoussion In Table III a summa ry of the results of the permanganate degradations of the various samples of propene is presented. ~ince the ntGchanism of permanganate oxidation of propene, the reliability of this oxidation as an analytical proce- dure, and tloe nature of' the labelling of the propene could not be determined independently, it will be necessary to examine the data in this table from these three points of view. The fact that different specific activites were found in the various fractions from propen~ prepared by different methods proved tha t rearrangement of the d oub Ie bO":ld to equilibrium did not occur during the analysis. Inspection of experimeLts I, 2, and 3 srows that extensive migration of the double bond occurred duri1l6 the pnparation by these methods and, in fact, the propene pr-:..duced in experiments land 3 consisted of equilibrium mixtures of l-C14_pro?ene~'1 and 3-C14_propene-1. However. the propene darived from the quaternary ammonium base (experiment 4) showed little, if any, ra- arrangement of the double bond and the product consisted, almost entirely, of' l-C14_propene-1. The mechanism which h8S been assul1led for the oxidative splitting of olefins 'iiith permanganate consipts of rupture of the molecule & t tr. e doublo bond with the production of acetic and carbonic acids in the case of propene. If the acetic acid is to be used as a measure of labelling of the methyl group of' propene, it is necessary to demonstrate that all tre Cl4 activity is present -----_._-- 7. J. U. Nef, Annalen, 309, 126 (1899). " .. Table III Ac5d Pcrm3n~anate A~alyses of nropene Samples -.,- .f, I -._... ---,--...'.---..-----'...... '...... _ ..._._.~ Expt. 1 Expt. 2 Expt. 3 Expt. 4 ~ith Dohydration 1jdth Dehydrltion with Preparative DehydrQtion PyrolJsis of Procedure ~etaphosphoric Acid Alorco A1203 Laboratory prepared n-propyl trimethy) A1203 ammonium hydroxide __~_..~_ ._. ,__ - ,J _ 1 Specific Activity of C 4 I' in starting material L 6350 6350 63~0 8300 {c/m/millimole} l' __.... / . I _ .-- i IAcetic;Oxalic iAcetic IOxalic Acetic Oxalic CO ~cetic itOxali Fr~ction Analyzed • CO2 Acid I Acid C02 f Acid Acid C02 Acid Acid 2 Acid ~c. - Specific Activ~ty of C14 in 279011610 : 1560 3980 I 1100 . 2130 2840' 1530 }' 2020 7600 130 bSlo Fr3ction (elm/millimole c) ! I I : . . .I I 1 ~ tot~l 14 ~ 9~ of C recovered I 41j 42 I 5.0 59 I 24 L 5.9 38 1 39 I 6.2 . 2.2 1. 5.7 1n Fr'3ctlon "* i; i .. I I I 1. 11 )'oles/mole C3 6 II 0.94 i 0.83 I 0.10 I 0.9: t 0.70 L0.09. . 0.8i 0.81 I 0.10 1'1 0.71 i 1M)"? 1 Total c 4 Recovery 99 . ,II 88 I 89 1 83 I." . II I I Total C Recovery I 94 ! 84 I 89 85 I 1 I * In this calculqtion only t~e olof:n content of the gas sa~ple used in the ~~n04 analyses was taken into account. The presence of labelled butene and other olefins derived from the original labelled propanol SOMe yiel~s introduces error in the c31cu13tion of as well as in the specific activity of the various I l-' fractions. This error cannot be corrected, since neither the number of c14 labelled 3toms per molecule I-!'" nor the isomers were known. I -15- UCRL.. 19 ", in the methyl group of tre acetic add. Therefore, on pyrolysis of a sample : of barium acetate to acetonf; and Ba,003' the lat-ter should cO"ltain no C14. A sample of acetate from expe:'iment 2, when py:rolyzed showed -t;loat 5% of the 014 present was present in the carboxyl group. The pyrolysis of a sample of synthe tic methyl-labelled acetate (8) yielded li-2% of the total activity in the BaC03 which would correspond to 3-4% of the activity apparently being in the carboxyl group. Hence, the above result may be taken to mean that little, if any~ carboxyl activity is present and that the carboxyl group of the aoetate is de rived from the central carbon atom of the propene. 'i'herefor~), in every case shown in Table III, the spe,Hic activity of the methyl carbon of acetic acid may be obta ined by doubli.ng ~he specific activi ty shown for acetic a cid. If acetic a(:id is- bt~dned onl~r from splitting of propene at the double bond, t:ben a Cl".,e in Tl1ich thfJre is no activity in the acetate fraction would prove that all 1.'e labelling was at one ead of the propene. This is tb~ case in ex periment "- where only 310 of the CJ./.t activity was presant in the ['('etate. This particular oropl'1e s?l'11ple was che01;:ed by the ozonozation ana.lysis previf)us ly described and Xl" acthity c0uld be found in the acetate. Therefore, the propene produced in experiment 4 consisted of the isomer l-C14_propene-l to the extent of 97-100%, and acetic acid can arise only from the CH3-CH : portion of the molecule. Acco, dingly, acetate is the ~ost rel:able indicator of the activity of the CH3- posion in pro 'ene and this is true eve:l thou,)l aceJ~i,c acid is not recovered in lO~)< yield. ~" act~.vi 'rhe specif ty of the CO 2 fraction always was found t,) be lower than that calcu]~ ted on the basis of the specific activity of th<'3 acetate. 'rhus, in experiment I, thE, 3pecific activity of the starting propanol ras 6350 elm per millimole. Sine? all the 014 is located in the I-positlon in the propanol, ------...... -----_.----- B. S. Aronoff, V. liaas, B. A. Fries, to be published. -16- UCRL-l9 . the speoific activity of this particular oarbon atom is also 6350 o/m per milli- .. mole of oarbon. The speoific activity of the methylene oarbon of the propene is therefore 6350- (2 x 160) = 3130 clm per milltmole C, but the specifio aotivity found in the CO 2 fraotion was only 2790 c/m. In experiment 2 the results were simUarly 4150 clm versus 3980 elm; in experiment 4, 8040 elm versus 7600 o/m. ~ot These data indioate that the CO 2 carbon is exclusively derived from the methylene carbon; but probably from the methyl and central carbon atoms as well. Examination of the oxalic acid fraction revealed that the oxalate oontains the methylene carbon atom of propene. The possibility of one carbon oompounds being present in this residue has been considered already and has been elimin- ated. The possibility that relatively large amounts of some three carbon com- pounds might be present may be eliminated on the basis of the specific aotivity of the fraotionsc If this oxidizable residue were entirely a three oarbon compound, the specifio activity in the active position would be three times the value shown in Tarle III. In experiment 4, the specific activity reported, when multiplied by thr:le would giv·8 a result muoh higher than the original speoific activity present in the start~ng material. On the other hand, if the substance were a two carbon compound, the specifio aotivity in the labelled position oorresponds olosely to that known to be present in the methylene carbon. These :-esults demonstrate that some propene is sp:l.it at the CH3-CH bond, perhaps to the extent of 15-20%. The -OR = CH2 group is oxidized to oxalio aoid, while the CH3- group is split off as a one carbon oc"npound, presumably oxidized to CC~, alt!lough seme may not be oxidized beyond methanol or formalde hyde. The specifio aotivity of C14 in the C02 fraotion (representing the = CHZ group) is therefore low due to the CO 2 which arises from the methyl group and probably from the central carbon atom as well. In the alkaline oxidation of propylene glycol (1), the yield of C02 is over one mole per mole of glycol, while -17- UCRL-19 .. the acetate is lower and oxulate is higher U'un that obtained from the acid oxidation. This led to the performance of an al~aline oxidation on the pro- pene from experiment 4. Th8 oxide.tion was carriod out i.n the same manner as trose previously desoribed except the medium Nas .04 N in NaOH. The number of moles of C02, acetic acid, and oxalic acid obtained per mole of propene were 1.64, 0.33 and 0.16 respectively. The specific activities of theE'e three fracti.ons were respectively 3410, 560 and 4370 c/m per millimole of carbon. 'rhe yield of £ portion of it has come from carbon atoms other than the methylene group of the propene. ~uantitative estimates, based upon relative yields and specific activities, indicate that nearly half of the prepene has been completely oxi dized to carbon dioxide, the remainder going partly (1/3) to acetic acid and C02 and partly (1/6) to oxalic acid and C02. btUI another route of oxidation is required to account for the small amount of activity found in the acetate fraction. This can be accounted for by some symmetrical intermediate (retain- ing the methyl group) such as isopropyl alcohol or acetone,.8 thus have three, and probably four, paths through whioh nropene is oxidized by permanganate. (100) * CO 2 * (50) CO 2 The number in parenthesis indicates the percentage of the original specific activity to bQ found in the atom or compound so labelled. -18- UCRL-l9 In the aoid oxidation path I predominates (5/6) with paths II and III contributing minor and approximately equal parts. Somewhat similar conolusions " were deduced for the &lkaline permanganate oxidation of propionio acid by 1ahinsky and Ruben (9). On the basis of the acetio acid speoifio activity, the propene prepared wi th metaphosphoric acid was a 50-50 equilibrium mixture of the two forms of 14 labelled propene, the propene prepared from commeroial A1 203 was a 65% 1_0 _ propene-l and 35% 3-C14_propene-l mixture, the propene prepared from the lab- oratory A1203 was approximately a 50-50 equilibrium mixture; while the propene derived from the quaternary ammonium hydroxide was a 97% l-c14_propene-l and 3% 3-Cl4_propene-l mixture. Isomerization during olefin preparation by dehydrativG reactions is well known. Asinger (10) found double bond isomerization all along the oarbon chain when dehydrating dodeoanol with A1203. ,vith pure A1 203 ,the principal isomers were dodecene ..·l and 2; however, when acidic impurities were present, more or less, equimc'ar quantit,ies of all the isomprs wore found. Iso:JlJriza- tion was found at temperatures as low as 250°C, even though the dchyd':'ation reaotion wa s incomplete at this tempera ture. The mechanism proposed was based upon readdition, followed by splitting off, of water. iioidic impurities appar- ently aocelerat.; the readdttion of water. l\hHtignon at. al. (11) obtainod 15% butene-2 when dehydra ting n-butanol with pure A1203 and 90% butene..2 when using impure 11.1203. The is'}mers w(;)re determined by bromination "Ind fraotionating of the dibromides, PinG:;; (12) obtained 100% butene-l wjch pure A1203 and 99.6% ------_.. __•..__ .._. - ~-_._- ,------.- - --- 9. P. Nahinsk;;p.nd ~" Kune:,!" J. l,m. C}'em. SO,,, 10. F. Asinger, Be:~ <, 2§.E, ';'247 (121,8) ~ ,,_) 11. C. Me.tignon, li. lVlouNau and h. vode, 0omp':;. rend" ~, 973 (1933). 12. H. Pines, J. Am. 0hem. SOOt ~, 3892 (1930). -19- UCRL-19 butene-l with commercial A1203 in the dehydration of n-butanol. Bis products were analyzed by low temperature distillation. Pines believes the results of ..( Matignon et. ale disagree with his own because isomerization of the dibromides occurred during their distillation. In the present study isomerization of propene during dehydrative prepar~tion over Al203 appeared to occur quite readilyl Tbis ease of isomerization may be due to the symmetrical structure of propene. The pr6paration of olefins by dehydration of alcohols with metaphosphoric acid also gave rise to general isomerization of the double bond along the chain in the case of dodecene (10). Morgan and Hickinbottom (15) obtained only butene-2 from n-butanol. In the experiments reported here complete equilibra- tion of propene isomers was found. Pyrolysis of n-propyltrimethylammonium hydroxide gave essentially pure l-C14_propene-l in 90% yield. A side reaction of this pyrolysis results in the formation of methanol and a mixed tertiary amine. von Braun (14) found 0"10% methanol while ~lanharJ.. and Ingold (15) and Ingold and Vasa (16) obtained 16-19% methanv::' on Pll'olysis of the above quaternary base. The yield 0"> pro- pene in the pNsent experiment f'a 11s between these two sets of resul's., This procedure appears to be a good, general, preparative method since th0 yields of olefins although falling off witr higher olefins, does ~ot drop b610w 70% even in the case of octene (16). ------,------.---_._'--- 13. G. T. rv:orr",:")u ar.: v~. J !.iick)(bottom, J. ~~.1'm. ~oc., Trans., _73, 97 (1923). 14. J. von Braun, .rl.nn., 3 ,,:, 1 ()'1l'.), 15. IV. Hanhart and C, K.J:.1go1d; j. vbem. SOJ" 997 (1927). 16. C. K. Ingold and C. C.' N. Vass, J. Cham. ~oc., 3125 (1928). -20- UGRL-19 Summary. l-C14-lpropene-l has been prepared. fre migration of the double bond under a variety of experimental conditions in the preparation of propene has been investigated. £he mechanism of the permanganate oxidation of the labelled propene has been examined. It has been found to proceed by several patbs the relative importance of which depends upon the experimental conditions, especially the pH. This paper is based on work performed under Contract Number \!-7405-eng-48 With the Atomic Energy Comnlission in connection with the Radiation Laboratory of the University of California, Berkeley, California.